Preparation, Characterization And Properties Of Poly - γ - Glutamic Acid / Chitosan Composite Membrane

Poly-γ-glutamic acid is a Polymer material of amino acid homopolymer having large number of amide bonds in molecule and intermolecular hydrogen bonds.It is formed by the amide bond linkage between the amino group of one glutamic acid and the carboxyl group of the next glutamic acid. Meanwhile,it is a polyanionic biopolymer that has many carboxyl groups. The molecular structure makes it has flocculability and biodegradability and has been successfully utilized in wastewater treatment,medicine,agriculture etc.Due to the high flocculability and nontoxicity,γ-PGA has been widely utilized in wastewater treatment,especially in wastewater containing heavy metal ions. However, due to the use of poly-γ- glutamic acid alone can not be reused will be a waste of resources and can only be positive ion adsorption.Therefore,γ-PGA crosslinking with chitosan produce a adsorbed film that can be reused.Main point as follows:1)Poly-γ-glutamic acid is produced by microbiological fermentation and being authenticated by paper chromatography、infrared spectroscopy scanning method、X-ray diffraction method combine with our laboratory ferment experience.γ-PGA is used in the future experiment.2)γ-PGA was crosslinked with chitosan to produce adsorbed film.The preparation technology:γ-PGA-CS mass ratio was 1:4,the mass sum was 0.1g,3mL deionized water,1.5mL 10% HAc volume,1mL glycerol,60℃ drying to produce adsorbed film.The composite membrane has been characterized by water absorption test,water retention test,cold field emission.3)The adsorption condition of γ-PGA composites with Cu2+、Pb2+ and the condition of desorption were studied.The optimum condition of γ-PGA composites with Cu2+50-70mg/L initial mass concentration,0.4g/L composite membrane,pH 5,the optimal temperature was 25 ℃,the reaction time was 1h.The optimum condition of γ-PGA composities with Pb2+50-60mg/L initial mass concentration,0.4g/L composite membrane,pH 3,the optimal temperature was 25℃,the reaction time was 1h.The optimal pH of desorption with Cu2+ was 4,during four successive cycles of operation,only 5%loss in adsorption efficiency of γ-PGA composites was shown.The optimal pH of desorption with Pb2+ was 3,during three successive cycles of operation,only 10% loss in adsorption efficiency of γ-PGA composites was shown.4)During fitting thermodynamic equation and kinetic equations,the result indicated that Redlich-Peterson and pseudo second order model had a better explain for the adsorption process.It was shown that γ-PGA composites had good adsorption capability with Cu2+ and Pb2+.It can be used more than three times with little loss.Besides,the adsorption film was non-toxic,biodegradable,edible and production of simplie,so it can be widely produced industrializedly as green product.